From 08a6f22ef6f843d0ea7252087787b5ab04610bec Mon Sep 17 00:00:00 2001 From: Matt Smith Date: Wed, 1 Sep 2021 12:44:37 -0700 Subject: [PATCH 1/3] libbpf: Change bpf_object_skeleton data field to const pointer This change was necessary to enforce the implied contract that bpf_object_skeleton->data should not be mutated. The data will be cast to `void *` during assignment to handle the case where a user is compiling with older libbpf headers to avoid a compiler warning of `const void *` data being cast to `void *` Signed-off-by: Matt Smith Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20210901194439.3853238-2-alastorze@fb.com --- tools/lib/bpf/libbpf.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index f177d897c5f7..2f6f0e15d1e7 100644 --- a/tools/lib/bpf/libbpf.h +++ b/tools/lib/bpf/libbpf.h @@ -854,7 +854,7 @@ struct bpf_object_skeleton { size_t sz; /* size of this struct, for forward/backward compatibility */ const char *name; - void *data; + const void *data; size_t data_sz; struct bpf_object **obj; From a6cc6b34b93e3660149a7cb947be98a9b239ffce Mon Sep 17 00:00:00 2001 From: Matt Smith Date: Wed, 1 Sep 2021 12:44:38 -0700 Subject: [PATCH 2/3] bpftool: Provide a helper method for accessing skeleton's embedded ELF data This adds a skeleton method X__elf_bytes() which returns the binary data of the compiled and embedded BPF object file. It additionally sets the size of the return data to the provided size_t pointer argument. The assignment to s->data is cast to void * to ensure no warning is issued if compiled with a previous version of libbpf where the bpf_object_skeleton field is void * instead of const void * Signed-off-by: Matt Smith Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20210901194439.3853238-3-alastorze@fb.com --- tools/bpf/bpftool/gen.c | 31 +++++++++++++++++++------------ 1 file changed, 19 insertions(+), 12 deletions(-) diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c index d40d92bbf0e4..e3ec47a6a612 100644 --- a/tools/bpf/bpftool/gen.c +++ b/tools/bpf/bpftool/gen.c @@ -238,8 +238,8 @@ static void codegen(const char *template, ...) } else if (c == '\n') { break; } else { - p_err("unrecognized character at pos %td in template '%s'", - src - template - 1, template); + p_err("unrecognized character at pos %td in template '%s': '%c'", + src - template - 1, template, c); free(s); exit(-1); } @@ -406,7 +406,7 @@ static void codegen_destroy(struct bpf_object *obj, const char *obj_name) } bpf_object__for_each_map(map, obj) { - const char * ident; + const char *ident; ident = get_map_ident(map); if (!ident) @@ -862,6 +862,8 @@ static int do_skeleton(int argc, char **argv) codegen("\ \n\ \n\ + static inline const void *%1$s__elf_bytes(size_t *sz); \n\ + \n\ static inline int \n\ %1$s__create_skeleton(struct %1$s *obj) \n\ { \n\ @@ -943,10 +945,20 @@ static int do_skeleton(int argc, char **argv) codegen("\ \n\ \n\ - s->data_sz = %d; \n\ - s->data = (void *)\"\\ \n\ - ", - file_sz); + s->data = (void *)%2$s__elf_bytes(&s->data_sz); \n\ + \n\ + return 0; \n\ + err: \n\ + bpf_object__destroy_skeleton(s); \n\ + return -ENOMEM; \n\ + } \n\ + \n\ + static inline const void *%2$s__elf_bytes(size_t *sz) \n\ + { \n\ + *sz = %1$d; \n\ + return (const void *)\"\\ \n\ + " + , file_sz, obj_name); /* embed contents of BPF object file */ print_hex(obj_data, file_sz); @@ -954,11 +966,6 @@ static int do_skeleton(int argc, char **argv) codegen("\ \n\ \"; \n\ - \n\ - return 0; \n\ - err: \n\ - bpf_object__destroy_skeleton(s); \n\ - return -ENOMEM; \n\ } \n\ \n\ #endif /* %s */ \n\ From 980a1a4c342f353a62d64174d0a6a9466a741273 Mon Sep 17 00:00:00 2001 From: Matt Smith Date: Wed, 1 Sep 2021 12:44:39 -0700 Subject: [PATCH 3/3] selftests/bpf: Add checks for X__elf_bytes() skeleton helper This patch adds two checks for the X__elf_bytes BPF skeleton helper method. The first asserts that the pointer returned from the helper method is valid, the second asserts that the provided size pointer is set. Signed-off-by: Matt Smith Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20210901194439.3853238-4-alastorze@fb.com --- tools/testing/selftests/bpf/prog_tests/skeleton.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/tools/testing/selftests/bpf/prog_tests/skeleton.c b/tools/testing/selftests/bpf/prog_tests/skeleton.c index f6f130c99b8c..fe1e204a65c6 100644 --- a/tools/testing/selftests/bpf/prog_tests/skeleton.c +++ b/tools/testing/selftests/bpf/prog_tests/skeleton.c @@ -18,6 +18,8 @@ void test_skeleton(void) struct test_skeleton__data *data; struct test_skeleton__rodata *rodata; struct test_skeleton__kconfig *kcfg; + const void *elf_bytes; + size_t elf_bytes_sz = 0; skel = test_skeleton__open(); if (CHECK(!skel, "skel_open", "failed to open skeleton\n")) @@ -91,6 +93,10 @@ void test_skeleton(void) CHECK(bss->kern_ver != kcfg->LINUX_KERNEL_VERSION, "ext2", "got %d != exp %d\n", bss->kern_ver, kcfg->LINUX_KERNEL_VERSION); + elf_bytes = test_skeleton__elf_bytes(&elf_bytes_sz); + ASSERT_OK_PTR(elf_bytes, "elf_bytes"); + ASSERT_GE(elf_bytes_sz, 0, "elf_bytes_sz"); + cleanup: test_skeleton__destroy(skel); }